1. Field of the Invention
This invention relates to the production of vinyl chloride polymers and more particularly, to a process for producing high-quality vinyl chloride polymers with high production efficiency.
2. Description of the Prior Art
In general, vinyl chloride polymers are produced by suspension polymerization of vinyl chloride monomer or mixtures comprising a major proportion of vinyl chloride monomer in an aqueous medium by use of monomer-soluble polymerization initiators. The monomer-soluble polymerization initiators used for this purpose greatly influence, depending on the type of initiator, the quality characteristics such as the exothermic pattern of the polymerization reaction, the polymerization time, the productivity, the scale deposit during polymerization, the initial coloration of polymer, the thermal stability, the odor, the non-extractability and the like.
In order to improve the productivity of vinyl chloride polymers, a recent trend is to shorten the polymerization time, with the tendency that polymerization initiators are now used in increasing amounts. As the amount of initiator is increased, there arise many problems including not only the limitation accompanied by the shortage in cooling capacity of overall existing polymerization apparatus, but also the initial coloration of polymer, the lowering of thermal stability, the generation of offensive odor owing to the increase in amount of the residue or decomposed product of polymerization initiator and the increase in amount of extracted components. In addition, the scale deposit within a polymerization vessel is also undesirably increased in amount.